Need help with portable AMP/DAC for a laptop/Notebook ( upgrading from FIIO E17).

I carry my MBP with me almost everywhere in a shoulder bag. Currently I use a FIIO E17 as my portable AMP/DAC with multiple different Headphones ( depending on the mood or time away from home), Sennheiser HD 650 , Beyerdynamic T1 , Phonak Audeo PFE 232 , Denon AH-D2000 , Sennheiser T50P , ... I also have a Fostex HP-P1 (iDevice AMP/DAC). I love the Fostex sound.Comparing to Fostex and even DacMagic Plus ( I own one ) my E17 sounds flat and lacks detail, maybe even muddy in the middle. My source is MOG, FLAC (I use Decibel) and CD. What is your suggestion for a portable AMP/DAC ?